Blends of modified radial polymers and engineering thermoplastic polymers

ABSTRACT

A super-tough polymeric composition comprising an engineering thermoplastic and a modified radial polymer. The engineering thermoplastic is selected from the group consisting of polyamides, thermoplastic polyesters, polyphenylene ether resins, polyarylene sulfide resins, polysulfone and the like. The modified radial polymer is modified by grafting a compound containing a carboxylic acid or carboxylic acid derivative group. The modified, radial polymer has from about 3 to about 50 arms, as determined using light scattering techniques and the arms will be olefin polymers. The polymer compositions will yield shaped articles which fail ductilely when tested using ASTM procedure D-256 at room temperature and some at -20° F.

FIELD OF THE INVENTION

This invention relates to a polymer composition. More particularly, thisinvention relates to a polymer composition comprising an engineeringthermoplastic and a functionalized radial polymer.

BACKGROUND OF THE INVENTION

Thermoplastic resins such as the polyamides, the thermoplasticpolyesters, the polyphenylene ether resins, the polyarylene sulfideresins, the polysulfones and the like are, of course, well known in theprior art. As is also well known in the prior art, these thermoplasticresins generally exhibit a combination of properties including excellentmechanical properties, good high heat resistance and good durabilitymaking them particularly useful for the preparation of molded, cast andextruded mechanical and electrical parts. These resins do not, however,lend themselves to utility in those areas requiring good impactresistance since, generally, they exhibit poor impact resistance.

In light of the several particularly good properties associated with theaforementioned thermoplastic resins, considerable effort has beenexpended in attempts to improve the impact resistance of the variousthermoplastic resins without impairing the other desirable propertiesthereof. In general, these attempts involve the incorporation of a lowmodulus rubber into a composition comprising the thermoplastic resin. Itis, of course, important that the low modulus rubber not separate fromthe thermoplastic resin during thermoplastic processing operations. Itis, then, important that the low modulus rubber either be compatiblewith the thermoplastic resin or contain one or more reactive groupswhich will either chemically or physically bond the low modulus rubberto the thermoplastic resin thereby preventing subsequent separation ofthe two polymers.

As a practical matter, it is, at best, difficult, if not impossible, tofind low modulus rubbers that are compatible with a broad range ofthermoplastic resins. As a result, most of the efforts to solve theimpact resistance problems of the aforementioned thermoplastic resinshas been made with elastomers that are either directly prepared or aremodified to contain one or more functional groups that will, in someway, bond with one or more groups contained in the thermoplastic resinused in the composition.

An early attempt to produce thermoplastic resin compositions havingimproved impact resistance with random type elastomers, which attempthas had some degree of commercial success, at least where a polymermodified with an acid or acid derivative is used as the impact modifier,is taught in U.S. Pat. No. 4,172,859 when a thermoplastic polyester orpolycarbonate is the thermoplastic resin and in U.S. Pat. No. 4,174,358when a polyamide is the thermoplastic resin. As is well known,thermoplastic resin compositions within the scope of the disclosure ofthese two patents frequently can be classified as "super-tough" at roomtemperature, but the amount of modifying polymer required sometimesexceeds that allowable for a composition having good tensile modulus andacceptable flexural modulus and yield stress. Moreover, while certain ofthe compositions can be classified as "super-tough" at room temperaturethere is little or no improvement in the impact resistance attemperatures below room temperature. As used herein, the recitation"super-tough" means that a sample of the composition failed ductilely,as opposed to brittlely, at the temperature tested using the notchedIzod toughness test (ASTM-D256) for 1/8 inch specimen.

In light of these prior art efforts failure to consistently producesuper-tough compositions having good tensile modulus and yield stress aswell as good low temperature impact properties, the need for anengineering thermoplastic composition having improved impact resistanceeven at lower temperatures and good flexural modulus at all temperaturesand a method for preparing such an improved composition is believed tobe readily apparent.

SUMMARY OF THE INVENTION

It has now been discovered that the foregoing and other disadvantages ofthe prior art engineering thermoplastic compositions can be avoided, orat least substantially reduced, with the engineering thermoplasticcomposition of this invention. It is, therefore, an object of thisinvention to provide an engineering thermoplastic composition. It isanother object of this invention to provide such an engineeringthermoplastic composition which will be "super-tough", at least at roomtemperature, and exhibit good flexural modulus over a relatively broadrange of relative engineering thermoplastic and elastomer concentrationsand at relatively lower modifier concentrations. It is still anotherobject of this invention to produce such an engineering thermoplasticcomposition which will exhibit "super-tough" characteristics at least atroom temperature and maintain most, if not all, of the properties of theengineering thermoplastic without significant impairment thereof. Theforegoing, and other, objects and advantages will become apparent fromthe description of the invention set forth hereinafter and the examplesincluded therein.

In accordance with the present invention, the foregoing, and other,objects and advantages are accomplished by incorporating a modifiedradial polymer having a plurality of olefin polymer arms into acomposition comprising an engineering thermoplastic polymer, whichengineering thermoplastic when used neat exhibits poor impactresistance. The radial polymer is modified by grafting carboxylic acidor carboxylic acid derivative functionality to the olefin polymer arms.The modified radial polymer is incorporated into the polymer compositionas an impact modifier. As indicated more fully hereinafter, variousparameters of the modified radial polymer pertinent with respect to theproduction of "super-tough" compositions must be controlled so as toproduce compositions which are "super-tough" at least at roomtemperature. These parameters include the amount of carboxylic acidand/or carboxylic acid derivative functionality incorporated into theradial polymer, the molecular weight of the radial polymer and theamount of the radial polymer incorporated into the engineeringthermoplastic composition.

DETAILED DESCRIPTION OF THE INVENTION

As just indicated supra, the present invention relates to a polymericcomposition comprising an engineering thermoplastic polymer, whichengineering thermoplastic polymer when used neat exhibits poor impactresistance, and a modified radial polymer, which radial polymer is usedas an impact modifier for the engineering thermoplastic polymer. Theradial polymer comprises a plurality of olefin polymer arms and ismodified by grafting carboxylic acid or carboxylic acid derivativefunctionality onto the olefin polymer arms. As indicated more fullyinfra, those variables which must be controlled to produce a"super-tough" composition will be controlled so as to produce asuper-tough composition. A composition will be super-tough as thatrecitation is used herein when a 1/8 inch shaped article fashionedtherefrom fails in a ductile as opposed to brittle manner when tested atroom temperature to determine its 1/8" notched Izod value usingASTM-D256 test procedure. Generally, the notched Izod value associatedwith ductile failure of the 1/8 inch specimen will be at least about 10ft lb/in. As indicated more fully infra, the method of failure may vary,and generally does, with the temperature at which the test procedure isused. For that reason, then, an article fashioned from the polymericcomposition of this invention shall be considered super-tough if thefailure at room temperature is ductile. In this regard, it should benoted that many of the compositions within the scope of this inventionwill yield articles which fail ductilely at temperatures as low as about-30° C. To avoid confusion, then, compositions failing at temperaturesbetween about -5° C. to about -30° C. and particularly between about-15° C. to about -25° C. will be referred to herein as compositionshaving surprising low temperature impact properties.

In general, any of the engineering thermoplastic polymers known toexhibit poor impact strength when used neat in molded articles can beused in the polymeric composition of this invention. Suitableengineering thermoplastic polymers, then include, but are notnecessarily limited to the polyamides, the thermoplastic polyesters, thepolyphenylene ether resins, the polyarylene sulfide resins, thepolysulfones and the like.

By polyamide is meant a condensation product which contains recurringaromatic and/or aliphatic amide groups as integral parts of the mainpolymer chain, such products being known generically as "nylons." Thepolyamide matrix of the toughened compositions of this invention is wellknown in the art and embraces those semi-crystalline and amorphousresins having a molecular weight of at least 5000 having a linear orbranched structure. These polyamides include α-polyamides andα,ω-polyamides. These polyamides have molecular weights of from about5,000 to about 50,000. Furthermore, the polyamides are preferably linearwith a melting point in excess of 200° C.

By "α-polyamides" is meant those polyamides having only one terminalgroup which strongly interacts or is reactive with the carboxylfunctional groups of the block copolymer utilized in the compositionsherein, such as an amine group. Examples of such α-polyamides are thosepolyamides that may be obtained by polymerizing a monoaminocarboxylicacid or an internal lactam thereof having at least two carbon atomsbetween the amino and carboxylic acid groups thereof. Suitablepolyamides include those described in U.S. Pat. Nos. 2,071,250;2,071,251; 2,241,322; and 2,312,966.

As examples of the said monoaminocarboxylic acids or lactams thereofthere may be mentioned those compounds containing from 2 to 16 carbonatoms between the amino and carboxylic acid groups, said carbon atomsforming a ring with the --CO--NH-- group in the case of a lactam. Asparticular examples of aminocarboxylic acids and lactams there may bementioned ε-aminocaproic acid, butyrolactam, pivalolactam, caprolactam,capyryllactam, enantholactam, undecanolactam, dodecanolactam and 3- and4-amino benzoic acids.

Illustrative examples of α-polyamides include:

polypyrrolidone (nylon 4)

polycaprolactam (nylon 6)

polyheptolactam (nylon 7)

polycapryllactam (nylon 8)

polynonanolactam (nylon 9)

polyundecanolactam (nylon 11)

polydodecanolactam (nylon 12)

It is also possible to use in this invention polyamides prepared by thecopolymerization of two or more of the above polymers orterpolymerization of the above polymers or their components.

By "α,ω-polyamides" is meant those polyamides having at least twoterminal groups, e.g. on each end of a linear polyamide, which stronglyinteract or are reactive with the carboxyl functional groups of theblock copolymer utilized in the compositions herein. Preferably, theseterminal groups are amines. Examples of such α,ω-polyamides are thosepolyamides that may be obtained by polymerizing a diamine which containsat least two carbon atoms between the amino groups thereof and adicarboxylic acid or ester thereof. Suitable α,ω-polyamides includethose described in U.S. Pat. Nos. 2,071,250; 2,071,251; 2,130,523;2,130,948; and 3,393,210, the disclosures of which are hereinincorporated by reference.

Typically, these polyamides are prepared by polymerizing substantiallyequimolar proportions of the diamine and the dicarboxylic acid.Furthermore, excess diamine may be employed to provide an excess ofamine end groups over carboxyl end groups in the polyamide.

The term "substantially equimolecular proportions" (of the diamine andof the dicarboxylic acid) is used to cover both strict equimolecularproportions and the slight departures therefrom which are involved inconventional techniques for stabilizing the viscosity of the resultantpolyamides.

Examples of the said diamines are diamines of the general formula H₂N(CH₂)_(n) NH₂ wherein n is an integer of from 2 to 16, such astrimethylenediamine, tetramethylenediamine, pentamethylenediamine,octamethylenediamine, decamethylenediamine, dodecamethylenediamine,hexadecamethylenediamine, and especially hexamethylenediamine.

C-alkylated diamines, e.g. 2,2-dimethylpentamethylenediamine and 2,2,4-and 2,4,4-trimethylhexamethylenediamine are further examples. Otherdiamines which may be mentioned as examples are aromatic diamines, e.g.p-phenylenediamine, 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenylether and 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenyl ether and4,4'-diaminodiphenylmethane; and cycloaliphatic diamines, for examplediaminodicyclohexylmethane.

The said dicarboxylic acids may be aromatic, for example isophthalic andterephthalic acids. Preferred dicarboxylic acids are of the formulaHOOC--Y--COOH wherein Y represents a divalent aliphatic radicalcontaining at least 2 carbon atoms, and examples of such acids aresebacic acid, octadecanedioic acid, suberic acid, azelaic acid,undecanedioic acid, glutaric acid, pimelic acid, and especially adipicacid. Oxalic acid is also a preferred acid. Furthermore, thedicarboxylic acid may be used in the form of a functional derivativethereof, for example an ester.

Illustrative examples of α, ω-polyamides include:

polyhexamethylene adipamide (nylon 6,6)

polyhexamethylene azelaiamide (nylon 6,9)

polyhexamethylene sebacamide (nylon 6,10)

polyhexamethylene isophthalamide (nylon 6,iP)

polyamide of hexamethylenediamine and n-dodecanedioic acid (nylon 6,12)

polyamide of dodecamethylenediamine and n-dodecanedioic acid (nylon12,12).

Other α,ω-polyamides may be prepared by the copolymerization of two ormore of the above polymers or terpolymerization of the above polymers ortheir components.

Another α,ω-polyamide is the nylon produced by Dynamit Nobel, which isthe product of the dimethyl ester of terephthalic acid and a mixture ofisomeric trimethyl hexamethylenediamine.

Thermoplastic polyesters that may be modified in the present inventioninclude polymers having recurring ester linkages as an integral part ofthe main polymer chain. Thermoplastic polyesters which may be used inthe compositions of this invention include, but are not necessarilylimited to, those having a weight average molecular weight of at leastabout 5,000 and a glass transition temperatures of at least about 25° C.Useful polyesters, then, include, but are not necessarily limited to,those described in U.S. Pat. No. 4,172,859, the disclosure of which isincorporated herein by reference. Thermoplastic polyesters which may beused in the compositions of this invention may be linear or branched andmay be crystalline or amorphous. Useful polyesters include thoseprepared by condensing a polycarboxylic acid, particularly adicarboxylic acid, or a derivative thereof and a polyalcohol,particularly a dialcohol. The polycarboxylic acid or derivative thereofused to prepare the polyester may be aromatic or aliphatic. Particularlyuseful polyesters include the poly(alkylene aryllates) particularly thepoly(alkylene terephthalates), the polylactones and the thermoplasticcellulosic esters and the like.

Polyphenylene ethers which may be modified so as to produce acomposition within the scope of the present invention includecondensation polymers which may be substituted in the two and sixpositions and graft copolymers of such polyphenylene ethers, wherein thegrafting is accomplished with styrene and substituted styrene-typemonomers. The substitution on the two and six carbon atoms of the phenylgroup may be aliphatic, generally having from one to about four carbonatoms or halogen. If desired, other graftable monomers may be combinedwith the styrene type monomer when a graft copolymer is used.

Polyarylene sulfide polymers which may be included in the compositionsof this invention include homopolymers and copolymers having astructural unit represented by the following general formula:

    --[Ar--S]--

wherein Ar stands for a phenylene group or an alkyl substitutedphenylene group. When the phenylene group is alkyl substituted, thealkyl group will, generally, contain from one to about 10 carbon atoms.

Thermoplastic polysulfones which may be used in the compositions of thisinvention include polymers having repeating phenylene groups bonded toSO₂. The phenylene groups contained in the polymer may, occasionally, bebonded to each other through an oxygen atom but repeating SO₂ groups areessential. In general, the thermoplastic polysulfones will have a weightaverage molecular weight of at least 5,000.

The hydrogenated radial polymers useful as modifiers in the compositionsof the present invention will comprise a plurality, at least three, andgenerally 3 to about 50 olefin polymer arms, preferably diolefin polymerarms, as determined using light scattering techniques. The olefinpolymer arms may be homopolymers or copolymers and an olefin,particularly a conjugated diolefin having from four to about twelvecarbon atoms, will preferably be used. Any of the nuclei known in theprior art to be useful in the production of radial polymers may be usedin preparing the radial polymers useful in the compositions of thisinvention. Suitable nuclei, then, include those which arenonpolymerizable and which contain a fixed number of reactive sites suchas those taught in copending U.S. patent application Ser. No. 45,686 aswell as those which are polymerizable such as the poly-alkenyl couplingagents taught in U.S. Pat. No. 3,985,830; Canadian Patent No. 716,645and British Patent No. 1,025,295, the disclosure of which applicationand patents are incorporated herein by reference. Radial polymers usefulas modifiers in the compositions of this invention may be prepared byfirst forming a living olefin polymer and then reacting the livingolefin polymer with a suitable coupling agent and thereafter, ifethylenic unsaturation remains, hydrogenating the resulting radialpolymer. Useful radial polymers may, then, be prepared using thetechniques summarized in U.S. Pat. Nos. 4,116,917 and 4,156,673, thedisclosure of which patents are herein incorporated by reference. Whenmonolefin polymers are used as the arms, certain cation catalysts knownin the prior art to be useful in preparing block copolymers will be usedand the arms connected to the coupling agent in the same manner as isused to couple polymers prepared with anionic catalyst. When the radialpolymer nucleus is formed with a compound having a fixed number ofreactive sites, the average number of arms in the polymer will,generally, be controlled by the number of reactive sites in the nucleus.When the nucleus is, however, polymerizable and therefore contains avariable number of reactive sites, the average number of arms in theradial polymer will, generally, be controlled by the relative amount ofliving polymer and nucleating agent actually combined. In general, theconjugated diolefin polymer arms used in the radial polymer incorporatedinto the compositions of this invention will have a weight averagemolecular weight within the range from about 2,000 to about 100,000 andwhen conjugated diolefin polymer are used as arms in the radial polymerthese will be hydrogenated so as to convert or saturate at least about80 percent of the initial ethylenic unsaturation contained in thepolymer. Preferably, the hydrogenation will be accomplished with thereaction product of an aluminum alkyl and a nickel carboxylate in amanner as taught in U.S. Pat. No. 3,700,633.

Polymers of the type which may be modified and then used as an impactmodifier in the compositions of the present invention are, of course,available commercially and, when desired, these commercially availablepolymers may be modified and used. To the extent that polymers withproperties different from those of the commercially available materialsare desired, however, preparation of the desired radial polymer will benecessary. In any case, after the radial polymer is in hand, it will benecessary to modify the same with a carboxylic acid or a carboxylic acidderivative before using the same as an impact modifier in thecompositions of the present invention.

In general, any carboxylic acid or derivative thereof having the abilityto react with the radial polymer in free radical initiated reactions areuseful to effect the modification needed for the compositions of thepresent invention. Useful modifying compounds may range frompolymerizable to nonpolymerizable compounds and are preferablynonpolymerizable or at least slowly polymerizable. Modification of theradial polymer may be accomplished in solution or in the melt via a freeradical mechanism.

While as just indicated supra, any carboxylic acid or acid derivativewhich may be grafted or otherwise reacted with the radial polymer may beused, the compound actually used will preferably contain slowlypolymerizable ethylenic unsaturation. When the compound actually used,then, is nonpolymerizable or slowly polymerizable, the grafting reactionwill favor the introduction of a single unit at each site ofintroduction. Also, preparation of a homopolymer of the compound usedfor the grafting which could ultimately separate from the othercomponents in the polymer composition will be avoided.

In general, essentially any carboxylic acid or carboxylic acidderivative could, initially, be incorporated into the radial polymer,even those containing groups which groups do not, per se, facilitateperformance of the modified, hydrogenated radial polymer as an impactmodifier so long as these groups can, ultimately, conveniently beconverted to a functional group which will facilitate performance of themodified polymer as an impact modifier. As a practical matter, however,groups that are particularly effective include the acid, per se, salts,anhydrides, esters, imides and amides. It is, of course, important thatthe functional group actually incorporated into the modified radialpolymer chemically react or at least physically bond to a functionalgroup contained in the engineering thermoplastic incorporated into thepolymer composition. In general, the compound containing the functionalgroup grafted to the hydrogenated radial polymer will be grafted in anamount within the range from about 0.1 to about 10, preferably fromabout 0.3 to about 5, and most preferably from about 0.5 to about 3,weight percent based on hydrogenated radial polymer. It will, of course,be appreciated that radial polymers containing a functional group,particularly a cyclic anhydride, within the preferred and most preferredranges, when incorporated into the composition at its most effectiveconcentration will result in compositions having surprising lowtemperature impact properties.

Useful compounds which may be grafted to the hydrogenated radial polymerinclude ethylenically unsaturated mono- and polycarboxylic acids andderivatives thereof, particularly dicarboxylic acids, containing fromabout three to about ten carbon atoms and preferably a single ethylenicunsaturation. Suitable derivatives include the corresponding anhydrides,salts, esters, ethers, amides, nitriles, thiols, thioacids, glycidyls,cyanides and the like. Examples of compounds which may be grafted to theradial polymer include acrylic acid, methacrylic acid, citraconic acid,maleic acid, fumaric acid, itaconic acid, corresponding anhydrides ofthese acids, esters of these acids wherein the alcohol moiety containsone to about 10 carbon atoms, glycidyl acrylate and methacrylate,cyanoacrylates, hydroxy substituted alkyl acrylates and methacrylateswherein said alkyl groups contain from one to about 10 carbon atoms, andthe like.

The modified radial polymer may be prepared using any of the techniquesknown in the prior art for preparing such polymers. For example, themodified radial polymer may be prepared using solution processes such asthose taught in U.S. Pat. Nos. 4,033,888; 4,077,893; and 4,670,173, thedisclosure of which patents are incorporated herein by reference, orwith melt-mixing processes such as those taught in U.S. Pat. Nos.4,427,828; 4,578,429; 4,628,072 and 4,657,971, the disclosure of whichpatents are incorporated herein by reference.

After the functionalization has been completed, it is advantageous toremove any excess, unreacted functionalizing agent since these materialscould compete with functionalizing groups incorporated into the polymerfor reaction with reactive groups in the engineering thermoplasticpolymers. This could, in turn, reduce the number of reactive sitesavailable for reaction with the modified hydrogenated radial polymerthereby reducing the effectiveness of the modified polymer as an impactmodifier.

The thermoplastic resin compositions of this invention may be preparedusing any of the techniques or equipment known in the prior art for thispurpose. The engineering thermoplastic or thermoplastics, in the casewhere more than one engineering thermoplastic is used, may be blendedwith the modified hydrogenated radial polymer or polymers, in the casewhere more than one radial polymer is used, then, with equipment such assingle and multiple screw extruders, mixing rollers, brabender mixers,banbury mills, kneaders and the like. When equipment of this type isused, the blending will be accomplished with the polymeric components inthe molten phase and at temperatures sufficiently high to maintain thiscondition. Alternatively, the polymeric components may be blended byforming a solution of the polymeric components in a suitable solvent andthen precipitating the polymer blend or evaporating the solvent. Thepolymeric blends of this invention may also be formed, simply, by drymixing of the two or more components.

In general, the thermoplastic resin compositions of this invention willcomprise from about 1 to about 50 parts (by weight) of one or moremodified hydrogenated radial polymers per 100 parts (by weight)engineering thermoplastic. As indicated supra, the thermoplastic resincompositions of this invention will, broadly, produce molded articleswhich fail ductilely when 1/8 inch specimen thereof are subjected totesting in accordance with ASTM D 256 at room temperature whilecompositions within the scope of the preferred embodiments will producemolded articles which will fail ductilely when tested in accordance withASTM procedure D 256 at or about temperatures as low as -30° C. Thecompositions of this invention will, then, be super-tough with respectto room temperature testing and compositions within the scope of thepreferred embodiment will exhibit surprising low temperature impactproperties.

As indicated supra, the critical parameters with respect to the impactresistance of molded articles prepared with any given engineeringthermoplastic or combination thereof for the compositions of thisinvention are: the particular functionalizing agent or agents selectedfor use in the modified radial polymer; the amount of functionalizingagent incorporated therein; and the amount of modified radial polymerincorporated into the thermoplastic resin composition and the molecularweight of the modified radial polymer or polymers. The value of each ofthese parameters required for a super-tough molded composition or amolded composition having surprising low temperature impact propertieswill also vary with the particular thermoplastic resin or resins used inthe composition. The extent of reaction or interaction between thefunctional groups of the modified radial polymer and the thermoplasticresin or resins contained in the composition as well as the particlesize of the modified, hydrogenated radial polymer dispersed phase in thecomposition may also affect the impact properties of articles moldedfrom a given composition but the affect of these variables is certainlynot clear at this time.

The thermoplastic resin compositions of this invention may also containother additives commonly used in such compositions. For example, thecompositions of this invention may contain fillers, reinforcing agents,thickeners and the like. When such agents are used, of course, they willbe used at concentrations well known in the prior art.

The compositions of the present invention may be molded or otherwiseformed into various types of shaped articles using conventionaltechniques well known in the prior art. The shaped articles will exhibitimproved impact resistance when compared to the same composition butwithout the impact modifier. Additionally, when the forementioned agentsare added to the compositions of the present invention, the amounts ofagents added reduce the impact resistance of shaped articles formedtherefrom such that the article is no longer supertough. However, theseshaped articles will still exhibit improved impact resistance whencompared to the same composition, but without the impact modifier, i.e.,the modified radial polymer.

Preferred Embodiment

In a preferred embodiment of the present invention, a modified,hydrogenated radial polymer having from about 15 to about 25 arms, asdetermined using light scattering GPC techniques, isoprene scale, willbe used to modify an engineering thermoplastic selected from the groupconsisting of polyamides and thermoplastic polyesters. The modified,hydrogenated radial polymer will be modified by grafting a compoundthereto containing a functional group selected from the group consistingof the carboxylic acid anhydrides, preferably cyclic anhydrides, havingfrom about 3 to about 10 carbon atoms and mixtures thereof, mostpreferably maleic anhydride. In the more preferred embodiment, themodified, hydrogenated radial polymer will be used as an impact modifierin a thermoplastic resin composition comprising a polyamide and in amost preferred embodiment the modified, hydrogenated radial polymer willbe used as an impact modifier in a thermoplastic resin compositioncomprising an α,ω-polyamide. In the preferred embodiment, the modified,hydrogenated radial polymer will comprise from about 0.3 to about 5weight percent of modifying compound, based on total polymer and eacharm in the modified, hydrogenated radial polymer will have a weightaverage molecular weight within the range from about 30,000 to about100,000. In the more preferred and most preferred embodiments, themodified radial polymer will contain from about 0.5 to about 3.0 weightpercent functional groups, based on total polymer and each arm of theradial polymer will have a weight average molecular weight within therange from about 30,000 to about 75,000. In the preferred embodiment, aconjugated diolefin having from 4 to about 10 carbon atoms will be usedto prepare the modified, hydrogenated radial polymer. In a morepreferred embodiment, the conjugated diolefin will be selected from thegroup consisting of butadiene, isoprene and mixtures thereof and in amost preferred embodiment the arms will be homopolymers and in the mostpreferred embodiments the arms of the modified, hydrogenated radialpolymer will be homopolymers of isoprene. In the preferred, morepreferred and most preferred embodiments, the initially unsaturatedpolymer will be hydrogenated so as to saturate at least 95% of theinitial ethylenic unsaturation. In the preferred embodiment, themodified radial polymer will be contained in the composition in anamount ranging from about 8 to about 35 parts (by weight) per 100 parts(by weight) engineering thermoplastic. In a most preferred embodiment ofthis invention, the modified radial polymer will be contained in thecomposition in an amount ranging from about 10 to about 25 parts (byweight) per 100 parts (by weight) engineering thermoplastic.

Having thus described the present invention, a preferred, more preferredand most preferred embodiment thereof, it is believed that the same willbecome even more apparent by reference to the following examples. Itwill be appreciated, however, that the examples are presented solely forpurposes of illustration and should not be construed as limiting theinvention.

EXAMPLE 1

In this example, an engineering thermoplastic resin composition wasprepared using a commercially available poly(butylene terephthalate) anda modified, hydrogenated radial polymer having, on average, 15hydrogenated polyisoprene homopolymer arms as determined using lightscattering techniques. The poly(butylene terephthalate) used was Valox310, which is available from General Electric. The modified,hydrogenated radial polymer was prepared by first forming a livingpolyisoprene homopolymer by polymerizing isoprene with an n-butyllithium catalyst to a weight average molecular weight of about 64,000and then reacting this living isoprene polymer with divinyl benzene. Theradial polymer was then hydrogenated in the presence of a catalystprepared by combining nickel 2-ethyl hexanoate and triethyl aluminum.The nickel 2-ethyl hexanoate and triethyl aluminum were combined in amole ratio of about 3:1 Ni:Al and the nickel 2-ethyl hexanoate contained0.5 moles water per mole of nickel 2-ethyl hexanoate. The hydrogenationwas completed at a time, temperature, hydrogen partial pressure andcatalyst concentration to enable hydrogenation of at least 98% of theethylenic unsaturation initially contained in the radial polymer. Aportion of this polymer was then grafted with 1.2 weight percent maleicanhydride by passing the polymer, maleic anhydride and a peroxidethrough a twin screw extruder at a temperature of about 260° C.Unreacted maleic anhydride was removed by pulling a vacuum on the moltenmodified polymer during the extruder grafting process. After themaleated, hydrogenated radial polymer was prepared, a polyester resincomposition (hereinafter referred to as Comp. No. 3) was prepared bycombining the poly(butylene terephthalate) and the maleated,hydrogenated radial polymer in a ratio of 70 parts (wt) polyester per 30parts (wt) of maleated, hydrogenated radial polymer. The polymers wereblended in the melt phase in a twin screw extruder. After the polymercomposition (Comp. No. 3) was prepared, a portion thereof was moldedinto 1/8 inch thick specimen suitable for testing using ASTM procedureD-256 to determine notched Izod values. Due to variations in the moldedstructure, notched Izod values were determined at both the dead end andgate end of the mold. For purposes of comparison, a polymericcomposition (hereinafter referred to as Comp. No. 2) was prepared usinga portion of the same poly(butylene terephthalate) and the unmaleatedhydrogenated radial polymer in the same ratios. A portion of this samplewas also molded into 1/8 inch thick specimen suitable for testing in thesame ASTM procedure and the notched Izod values of the molded structureagain determined. For purposes of further comparison, the poly(butyleneterephthalate) alone (hereinafter Comp. No. 1) was molded into a 1/8inch thick structure and the notched Izod values determined for thisspecimen using ASTM D 256 as well. The notched Izod values weredetermined at both room temperature and -20° F. The flexural modulus inMpsi was also determined for each of the specimen. The results actuallyachieved are set forth in the following Table:

    ______________________________________                                                 1/8" Notched Izod (ft lb/in)                                                                  Flex Mod                                             Comp. No. RT           -20° F.                                                                          (Mpsi)                                       ______________________________________                                        1         0.9          0.8       342                                          2         5.2/3.9      1.7/1.5   176                                          3         16.3/15.4    3.2/3.2   174                                          ______________________________________                                    

As will be apparent from the data summarized in the preceding table, thecomposition comprising a commercially available poly(butyleneterephthalate) and a maleated, hydrogenated radial polymer produced amolded structure which would be considered super-tough having 1/8"notched Izod values at room temperature above about 10 ft lbs/in. Thecomposition did not, however, exhibit surprising low temperature impactproperties due primaryly to the low amount of maleic anhydride in theradial polymer and the fact that the engineering thermoplastic was apolyester.

EXAMPLE 2

In this example, an engineering thermoplastic resin composition withinthe scope of the present invention was prepared with a commerciallyavailable nylon 6,6 and a maleated, hydrogenated radial polymeridentical to that used in Example 1. The nylon 6,6 actually used wasZytel 101 available from E. I. Dupont de NeMoures & Co. In thecomposition prepared in this example, the engineering thermoplasticresin composition within the scope of this invention contained 80 weightpercent of the nylon 6,6 and 20 weight percent of the maleated,hydrogenated radial polymer. After the composition was prepared, aportion thereof was molded into 1/8 inch thick specimens and the notchedIzod values determined at room temperature and -20° F. in the samemanner as was used in Example 1 except the samples were kept dry asmolded. The flexural modulus was also determined in the same manner aswas used in Example 1 except the samples were kept dry as molded. Forpurposes of comparison, these same values were determined for apolymeric composition prepared in the same manner as that within thescope of the present invention except that the unmaleated radial polymerwas substituted for the maleated radial polymer at the sameconcentration. Also for purposes of comparison, the 1/8" notched Izodvalue and flexural modulus of molded articles prepared with just thenylon 6,6 were determined. For purposes of convenience, the polymericcomposition within the scope of this invention is hereinafter referredto as composition no. 6, the composition prepared with the unmaleated,hydrogenated, radial polymer is identified as composition no. 5 and thecomposition prepared solely with the nylon 6,6 is identified ascomposition no. 4. The results obtained with each composition aresummarized in the following Table:

    ______________________________________                                                 1/8" Notched Izod (ft lb/in)                                                                  Flex Mod                                             Comp. No. RT           -20° F.                                                                          (Mpsi)                                       ______________________________________                                        4         0.8          0.7       440                                          5         0.9/0.9      0.6/0.6   285                                          6         18.6/18.4    --        248                                          ______________________________________                                    

As will be apparent from the data summarized in the preceding Table, asuper-tough composition was obtained with as little as 20 weight percentof the maleated, hydrogenated radial polymer. Also, while the flexuralmodulus of the compositions containing the modified, hydrogenated radialpolymer are less than those of the nylon 6,6 alone the flexural modulusactually obtained are adequate for most end use applications.

EXAMPLE 3

In this example, five engineering thermoplastic resin compositions wereprepared at five different concentrations of a maleated, hydrogenatedradial polymer. The engineering thermoplastic used in each of thecompositions was a nylon 6,6 identical to that used in Example 2. Themaleated, hydrogenated radial polymer used in each of the compositionsalso was identical to that used in Example 2. The compositions wereprepared in a manner identical to that used in Example 2 and, after eachcomposition was completed, the 1/8" notched Izod values at roomtemperature and -20° F. were determined in the same manner as was usedin Example 2 and the flexural modulus (Flex Mod) of each composition wasdetermined in Mpsi. The five compositions prepared contained themaleated, hydrogenated radial polymer at concentrations of 5, 10, 15, 20and 25 weight percent with the remainder being nylon 6,6 and forconvenience, these compositions are referred to hereinafter as Comp.Nos. 7-11, respectively. The results obtained with each composition aresummarized in the following Table:

    ______________________________________                                        Modifier      1/8" Notched Izod (ft-lb/in)                                                                  Flex Mod                                        Comp. No.                                                                             Wt %      RT        -20° F.                                                                        (Mpsi)                                    ______________________________________                                        7        5        2.2/2.2   1.4/1.4 335                                       8       10         3.5/12.2 2.3/2.5 291                                       9       15        16.0/16.8 3.7/4.3 265                                       10      20        19.2/19.2 14.8/16.4                                                                             235                                       11      25        19.7/19.3 19.0/19.6                                                                             194                                       ______________________________________                                    

As will be apparent from the data summarized in the preceding Table,compositions comprising a maleated, hydrogenated radial polymersurprisingly are super-tough at modifier concentrations as low as 10weight percent and exhibit surprising low temperature impact propertiesat concentrations as low as 20 weight percent. Also, the flexuralmoduli, while lower than that of the nylon 6,6 alone are adequate formost end use applications.

EXAMPLE 4

In this example, a series of engineering thermoplastic resincompositions were prepared at five different modified, hydrogenatedradial polymer concentrations. The engineering thermoplastic resin usedin each of the compositions was a nylon 6,6 identical to that used inExample 2 and 3 while the modified, hydrogenated radial polymercontained, on average, 17 arms, as determined by light scattering, ofpolyisoprene homopolymer having a weight average molecular weight ofabout 35,000. The isoprene polymer was prepared in a manner identical tothat used in Example 1 except that polymerization of the isoprene wasdiscontinued when the weight average molecular weight reached 35,000 andthe living isoprene homopolymers were then combined with divinyl benzenein the coupling step. The polymer was maleated in the same manner as wasused in Example 1 except that the amount of maleic anhydride used wasincreased such that the polymer ultimately contained 1.8 weight percentmaleic anhydride. Again, the compositions prepared in this examplecontained 5, 10, 15, 20 and 25 weight percent of the maleated,hydrogenated radial polymer and correspondingly 95, 90, 85, 80 and 75weight percent of the nylon 6,6. For convenience, these compositions areidentified hereinafter as Comp. Nos. 12-16, respectively. After eachcomposition was prepared, a portion thereof was molded into 1/8" thickspecimens and the notched Izod values at room temperature and at -20° F.determined in the same manner as was used in the previous examples.Similarly, the flexural modulus was also determined in Mpsi. Prior toincorporation into the polymeric composition, the maleated, hydrogenatedradial polymer was dried to a moisture content of 0.1 wt % in a vacuumat a temperature of 60° C. The results obtained in each of the examplesis summarized in the following Table:

    ______________________________________                                        Modifier      1/8" Notched Izod (ft-lb/in)                                                                  Flex Mod                                        Comp. No.                                                                             Wt %      RT        -20° F.                                                                        (Mpsi)                                    ______________________________________                                        12       5        2.0/2.4   1.2/1.4 356                                       13      10        2.6/3.1   2.0/2.5 289                                       14      15        11.3/12.5 3.0/3.4 270                                       15      20        18.0/17.4 4.0/4.5 200                                       16      25        21.3/19.8  9.4/13.0                                                                             183                                       ______________________________________                                    

As will be apparent from the data summarized in the preceding table,compositions comprising nylon 6,6 and the significantly lower molecularweight maleated, hydrogenated radial polymer again exhibited super-toughproperties at concentrations of maleated, hydrogenated radial polymer of15 weight percent and more. Also, the low temperature properties wereparticularly good for that composition containing 25 weight percent ofthe radial polymer. This is, of course, somewhat different than the lowtemperature properties of the compositions containing the highermolecular weight radial polymer and this difference is attributed solelyto the difference in molecular weight. As also is apparent from the datasummarized in the preceding table, the flexural modulus of the severalcompositions is lower than that of the nylon 6,6 alone, but all areadequate for most end uses of the compositions.

EXAMPLE 5

In this example, three engineering thermosplastic compositions wereprepared at different modified, hydrogenated radial polymerconcentrations. The engineering thermoplastic used in these compositionswas a nylon 6,6 identical to that used in Example 4 and the modified,hydrogenated radial polymer was a maleated polymer having isoprenehomopolymer arms identical to that used in Example 4 except that themodified polymer used in this example was dried to a moisture content of<0.1% w in a fluidized bed using nitrogen at 60° C. After thecompositions were completed, a portion of each was molded into 1/8"thick specimens and the notched Izod value determined at roomtemperature and -20° F. in the same manner as was used in the previousexamples. Also, the flexural modulus of each was determined in Mpsi. Thecompositions contained 15, 20 and 25 weight percent of the modifiedradial polymer and correspondingly 85, 80 and 75 weight percent of thenylon 6,6. For convenience, these compositions are identifiedhereinafter as Comp. Nos. 17-19. The results obtained with eachcomposition are summarized in the following Table:

    ______________________________________                                        Modifier      1/8" Notched Izod (ft-lb/in)                                                                  Flex Mod                                        Comp. No.                                                                             Wt %      RT        -20° F.                                                                        (Mpsi)                                    ______________________________________                                        17      15        13.5/14.4 3.1/3.6 264                                       18      20        19.5/20.0 5.4/8.5 220                                       19      25        20.9/20.0 15.2/16.9                                                                             192                                       ______________________________________                                    

As will be apparent from the data summarized in the preceding table, thecompositions prepared in this example all resulted in super-tough shapedarticles. Also, the low temperature properties of the compositioncontaining 25 weight percent modified, radial polymer were surprisinglygood and, in fact, were significantly better than the low temperatureproperties of the composition of example 4 containing 25 weight percentof the modified, radial polymer. This, then, suggests that the methodused to dry the modified, radial polymer could affect at least the lowtemperature inpact properties.

While the present invention has been described and illustrated byreference to particular embodiments thereof, it will be appreciated bythose of ordinary skill in the art that the same lends itself tovariations not necessarily discussed or illustrated herein. For thisreason, reference should be made solely to the appended claims forpurposes of determining the true scope of the present invention.

Having thus described and illustrated the invention, what is claimedis:
 1. A thermoplastic polymer composition comprising from about 1 toabout 50 parts (by weight) of a modified radial polymer having from 10to about 25 arms per molecule as determined using light scatteringtechniques, the modified radial polymer consisting of hydrogenatedconjugated diene units and grafted compounds selected from a groupconsisting of maleic anhydride, acrylic acid, methacrylic acid, maleicacid, and fumaric acid, per 100 parts (by weight) of an engineeringthermoplastic polymer selected from a group consisting of polyamides andthermoplastic polyesters.
 2. The polymer composition of claim 1 whereinsaid engineering thermoplastic polymer is a nylon 6,6.
 3. The polymercomposition of claim 2 wherein said modified radial polymer is presentat a concentration within the range from about 8 to about 35 parts (byweight) per 100 parts (by weight) of the nylon 6,6.
 4. The polymercomposition of claim 3 wherein said modified radial polymer consists ofthe hydrogenated conjugated diene units and from about 0.5 to about 3weight percent of grafted maleic anhydride, based on total modifiedradial polymer.
 5. The polymer composition of claim 4 wherein shapedarticles prepared with said polymer composition have a 1/8" notched Izodnumber as determined by ASTM procedure D-256 greater than 10 ft lb/in at-20° F.
 6. The polymer composition of claim 4 wherein shaped articlesprepared with said polymer composition fail ductilely as opposed tobrittlely when tested using ASTM procedure D-256 at -20° F.
 7. Thepolymer composition of claim 4 wherein said modified radial polymercontains from about 15 to about 25 arms per molecule, as determinedusing light scattering techniques.
 8. The polymer composition of claim 7wherein each of said arms have weight average molecular weights withinthe range from about 2,000 to about 100,000.
 9. The polymer compositionof claim 8 wherein said arms are hydrogenated isoprene homopolymer arms.10. The polymer composition of claim 8 wherein said molecular weight ofthe arms is within the range from about 30,000 to about 75,000.